# High-intensity interval training improves performance in young and older individuals by increasing mechanical efficiency

PMID: 28381445
Journal: Physiological Reports
Published: 2017-04-05
Authors: Jabbour G, Iancu HD, Mauriège P, Joanisse DR, Martin LJ

## Question

Does six weeks of short supramaximal cycling HIIT improve mechanical efficiency, peak power, energy expenditure, body composition, and VO2max in young and older sedentary adults?

## Summary

Six weeks of very short cycling sprints improved peak power and mechanical efficiency in healthy sedentary young and middle-aged/older adults, but did not improve VO2max. The study had no non-exercise control group and focused on laboratory physiology outcomes.

## Population

- Healthy sedentary young adults and healthy sedentary older adults.
- Sample size: 30
- Age: Young 26.2 +/- 2.4 years; older 54.5 +/- 2.3 years.
- Sex: Young 5M/12F; older 5M/8F.
- Fitness level: Sedentary, less than 60 minutes per week of structured exercise and no systematic training in the prior 6 months.
- Health status: Healthy, non-smoking adults without orthopedic, neurologic, cardiovascular, or chronic disease.

## Methodology

- Single-arm pre/post training study comparing responses in young and older age groups.
- 6 weeks
- Laboratory cycling intervention at the University of Moncton.

## Protocol

- Six-week supramaximal cycling HIIT.
- Modality: Cycle ergometer.
- Work intervals: 6 seconds supramaximal cycling.
- Recovery: 2 minutes passive recovery.
- Sets or repetitions: Six sprint repetitions per session.
- Intensity: Maximal velocity against resistance determined by force-velocity testing; resistance adjusted every 2 weeks.
- Session duration: About 16-18 minutes including 5-minute warm-up at 40-50% HRmax.
- Frequency: 3 sessions per week.
- Program length: 6 weeks; 18 sessions.
- Progression: Resistance adjusted every 2 weeks using repeated force-velocity testing.

## Outcomes

### Peak power
Status: improved
Peak power increased in both young and older groups.

Young Pmax 520 to 620 W; older 540 to 600 W; relative Pmax increased young 6.1 to 8.5 W/kg and older 6.1 to 7.1 W/kg; p < 0.01.

### Mechanical efficiency
Status: improved
Mechanical efficiency increased at VT1, VT2, and VO2max in both groups.

ME increases were significant at all assessed intensities (p < 0.01), with larger percentage gains in the older group at several thresholds.

### VO2max
Status: no clear change
VO2max did not change in either age group.

Authors reported no VO2max change after training.

### Older group body composition
Status: improved
The older group lost body mass and fat mass, while the young group did not change body mass.

Older body mass 90.1 to 87.1 kg, p < 0.01; fat mass 33.8 to 31.8.

## Practical Insights

- Very short sprints with long passive recovery can improve peak power and mechanical efficiency without increasing VO2max.
- For app messaging, this is better evidence for performance/efficiency mechanisms than for cardiorespiratory fitness gains.
- The 6-second sprint format is highly equipment- and testing-dependent.

## Limitations

- No non-exercise control group.
- Small sample.
- Short intervention.
- The older group averaged about 54.5 years, so it is not representative of elderly adults.
- Laboratory cycle ergometry and mechanical-efficiency outcomes limit direct translation.
- Diet and non-study activity were not tightly controlled.

## Safety And Adherence

- All participants completed all 18 sessions.
- The article stated no other difficulties were encountered.
- Participants were screened to exclude chronic disease and contraindicating conditions.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/28381445/) (pubmed)
- [DOI](https://doi.org/10.14814/phy2.13232) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5392519/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.